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Abstract:

A method of formatting a digital broadcast transport stream packet, a
digital broadcast transmitter, and a signal processing method thereof,
includes constructing a transport stream packet that includes a stuffing
region for an insertion of a known supplementary reference signal (SRS)
data therein, randomizing the packet that includes the stuffing region is
randomized, and the SRS data is inserted into the stuffing region of the
randomized packet. Adding a parity for an error correction to the packet
into which the SRS data has been inserted, the packet to which the parity
has been added is interleaved, and a trellis encoding of the interleaved
packet is performed. Inserting a segment sync signal and a field sync
signal into the trellis-encoded packet, and a vestigial side band (VSB)
modulation and an RF conversion of the packet are performed to transmit
the VSB-modulated and RF-converted packet.

Claims:

1. A digital broadcast receiver, comprising:a demodulator to receive a
stream, and to demodulate the received stream; andan equalizer to
equalize the demodulated stream,wherein the stream is received from a
digital broadcast transmitter to adjust a position of data of a
predetermined type included in the stream and a position to insert known
data, to insert the known data into the adjusted position, and to
interleave the known data using a transmission stream post multiplexer
and an interleaver.

2. The digital broadcast receiver of claim 1, wherein the data of the
predetermined type is one of a program clock reference, an original
program clock reference, a slice countdown, a transport private data
length, and an adaptation field extension length.

3. A method for processing a stream of a digital broadcast receiver,
comprising:receiving a stream;demodulating the stream; andequalizing the
demodulated stream,wherein the stream is received from a digital
broadcast transmitter to adjust a position of data of a predetermined
type included in the stream and a position to insert known data, to
insert the known data into the adjusted position, and to interleave the
known data using a transmission stream post multiplexer and an
interleaver.

4. The method of claim 3, wherein the data of the predetermined type is
one of a program clock reference, an original program clock reference, a
slice countdown, a transport private data length, and an adaptation field
extension length.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is a continuation of U.S. application Ser. No.
11/416,204, filed on May 3, 2006, now pending, which claims benefit of
U.S. Provisional Patent Application No. 60/683,304 filed on May 23, 2005
and U.S. Provisional Patent Application No. 60/724,898 filed on Oct. 11,
2005 in the United States Patent and Trademark Office, the disclosures of
which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]Aspects of the present invention relate to a method for formatting a
digital broadcast transport stream packet, a digital broadcast
transmitter, and a signal processing method thereof, and more
particularly to a method of formatting a digital broadcast transport
stream packet, a digital broadcast transmitter, and a signal processing
method thereof, which can improve the receiving performance of a
receiving system and maintain the compatibility with the existing system
by generating an adaptation field in a transport stream packet and
inserting known data (i.e., supplementary reference sequence (hereinafter
referred to as "SRS")) into the position of the adaptation field.

[0004]2. Description of the Related Art

[0005]An Advanced Television Systems Committee (ATSC) Vestigial Side Band
(VSB) system that is an American-type digital terrestrial broadcasting
system is a signal carrier type broadcasting system, and uses a field
sync signal in the unit of 312 segments. FIG. 1 is a block diagram
illustrating the construction of a transmitter/receiver of an ATSC DTV
standard as a general American-type digital terrestrial broadcasting
system. The digital broadcast transmitter of FIG. 1 includes a randomizer
110 for randomizing a Moving Picture Experts Group-2 (MPEG-2) transport
stream (TS), a Reed-Solomon (RS) encoder 120 for adding RS parity bytes
to the transport stream (TS) in order to correct bit errors occurring due
to the channel characteristic in a transport process. An interleaver 130
interleaves the RS-encoded data according to a specified pattern. A
trellis encoder 140 maps the interleaved data onto 8-level symbols by
performing a trellis encoding of the interleaved data at the rate of 2/3.
The digital broadcast transmitter performs error correction coding of the
MPEG-2 transport stream.

[0006]The digital broadcast transmitter further includes a multiplexer 150
to insert a segment sync signal and a field sync signal into the
error-correction-coded data. A modulator/RF converter 160 inserts a pilot
tone into the data symbols into which the segment sync signal and the
field sync signal are inserted by inserting specified DC values into the
data symbols, performs a VSB modulation of the data symbols by
pulse-shaping the data symbols, and up-converts the modulated data
symbols into an RF channel band signal to transmit the RF channel band
signal.

[0007]Accordingly, the digital broadcast transmitter randomizes the MPEG-2
transport stream, outer-codes the randomized data through the RS encoder
120 that is an outer coder, and distributes the coded data through the
interleaver 130. Also, the digital broadcast transmitter inner-codes the
interleaved data in the unit of 12 symbols through the trellis encoder
140, performs the mapping of the inner-coded data onto the 8-level
symbols, inserts the field sync signal and the segment sync signal into
the coded data, performs the VSB modulation of the data by inserting a
pilot tone into the data, and then up-converts the modulated data into
the RF signal to output the RF signal.

[0008]Meanwhile, the digital broadcast receiver of FIG. 1 includes a tuner
(not illustrated) for down-converting an RF signal received through a
channel into a baseband signal. A demodulator 220 performs a sync
detection and demodulation of the converted baseband signal. An equalizer
230 compensates for a channel distortion of the demodulated signal
occurring due to a multi-path transmission. A trellis decoder 240
corrects errors of the equalized signal and decodes the equalized signal
to symbol data. A deinterleaver 250 rearranges the data distributed by
the interleaver 130 of the digital broadcast transmitter. An RS decoder
260 corrects errors, and derandomizer 270 derandomizes the data corrected
through the RS decoder 260 and outputs an MPEG-2 transport stream.

[0009]Accordingly, the digital broadcast receiver of FIG. 1 down-converts
the RF signal into the baseband signal, demodulates and equalizes the
converted signal, and then channel-decodes the demodulated signal to
restore to the original signal.

[0010]FIG. 2 illustrates a VSB data frame for use in the American type
digital broadcasting (8-VSB) system, into which a segment sync signal and
a field sync signal are inserted. As shown in FIG. 2, one frame is
composed of two fields. One field is composed of one field sync segment
that is the first segment, and 312 data segments. Also, one segment in
the VSB data frame corresponds to one MPEG-2 packet, and is composed of a
segment sync signal of four symbols and 828 data symbols.

[0011]In FIG. 2, the segment sync signal and the field sync signal are
used for the synchronization and equalization in the digital broadcast
receiver. That is, the field sync signal and the segment sync signal
refer to known data between the digital broadcast transmitter and
receiver, which is used as a reference signal when the equalization is
performed in the receiver side.

[0012]As shown in FIG. 1, the VSB system of the American type digital
terrestrial broadcasting system is a single carrier system, and thus has
the drawback in that it is weak in a multi-path fading channel
environment having the Doppler effect. Accordingly, the performance of
the receiver is greatly influenced by the performance of the equalizer
for removing the multi-path fading. However, according to the existing
transport frame as shown in FIG. 2, since the field sync signal that is
the reference signal of the equalizer appears once for every 313
segments, its frequency is quite low with respect to one frame signal,
and this causes the performance of equalization to deteriorate.

[0013]That is, it is not easy for the existing equalizer to estimate the
channel using a small amount of data as above and to equalize the
received signal by removing the multi-path fading. Accordingly, the
conventional digital broadcast receiver has the disadvantages that its
receiving performance deteriorates in an inferior channel environment,
and especially in a Doppler fading channel environment.

SUMMARY OF THE INVENTION

[0014]An aspect of the present invention is to provide a method for
formatting a digital broadcast transport stream packet, and a signal
processing method for a digital broadcast transmitter, which can maintain
the compatibility with the existing digital broadcast
transmitting/receiving system.

[0015]Additional aspects and/or advantages of the invention will be set
forth in part in the description which follows and, in part, will be
obvious from the description, or may be learned by practice of the
invention.

[0016]The foregoing and other objects and/or advantages are substantially
realized by providing a method for formatting a digital broadcast
transport stream (TS) packet including a header and a payload which
comprises inserting known supplementary reference sequence (SRS) data
into the packet.

[0017]According to an aspect of the invention, the packet further includes
an adaptation field, and the SRS data inserted into at least a portion of
the adaptation field.

[0018]According to an aspect of the invention, the adaptation field
includes an option field selectively included, and the SRS data is
inserted into at least a portion of the adaptation field except for the
option field.

[0019]According to an aspect of the invention, the option field is at
least one of a program clock reference (PCR), an original program clock
reference (OPCR), a splice countdown, a transport private data length,
and an adaptation field extension length, or combinations thereof.

[0020]According to an aspect of the invention, the SRS signal is used for
a synchronization and/or a channel equalization.

[0021]In another aspect of the present invention, there is provided a
digital broadcast transmitter, which comprises a packet construction unit
for constructing a transport stream packet that includes a stuffing
region for an insertion of a known supplementary reference signal (SRS)
data therein; a randomizer for randomizing the packet that includes the
stuffing region; an SRS insertion unit for inserting the SRS data into
the stuffing region of the randomized packet; a Reed-Solomon (RS) encoder
for adding a parity for an error correction to the packet into which the
SRS data has been inserted; an interleaver for interleaving packet to
which the parity has been added; a trellis encoder for performing a
trellis encoding of the interleaved packet; a multiplexer for inserting a
segment sync signal and a field sync signal into the trellis-encoded
packet; and a modulator/RF converter for performing a vestigial side band
(VSB) modulation and an RF conversion of an output signal of the
multiplexer to transmit the VSB-modulated and RF-converted signal.

[0022]In still another aspect of the present invention, there is provided
a signal processing method for a digital broadcast transmitter, which
comprises constructing a transport stream packet that includes a stuffing
region for an insertion of a known supplementary reference signal (SRS)
data therein; randomizing the packet that includes the stuffing region;
inserting the SRS data into the stuffing region of the randomized packet;
adding a parity for an error correction to the packet into which the SRS
data has been inserted; interleaving packet to which the parity has been
added; performing a trellis encoding of the interleaved packet; inserting
a segment sync signal and a field sync signal into the trellis-encoded
packet; and performing a vestigial side band (VSB) modulation and an RF
conversion of the packet to transmit the VSB-modulated and RF-converted
packet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]These and/or other aspects and advantages of the invention will
become apparent and more readily appreciated from the following
description of the embodiments, taken in conjunction with the
accompanying drawings of which:

[0025]FIG. 2 is a view illustrating the structure of a conventional ATSC
VSB data frame;

[0026]FIG. 3 is a view illustrating the structure of a transport stream
packet;

[0027]FIG. 4 is a view illustrating the structure of a header of an
adaptation field of a transport stream;

[0028]FIG. 5a to 5e are views illustrating diverse data formats of an
MPEG-2 transport stream packet that includes an adaptation field to which
stuff bytes are added according to aspects of the present invention;

[0029]FIG. 6a is a block diagram illustrating the construction of a
digital broadcast transmitter according to an embodiment of the present
invention;

[0030]FIG. 6b is a block diagram illustrating the construction of a
digital broadcast transmitter according to another embodiment of the
present invention;

[0031]FIG. 7 is a view illustrating an input type of an MPEG packet
according to an aspect of the present invention;

[0032]FIG. 8 is an exemplary view illustrating the structure of an
interleaved packet according to an embodiment of the present invention;
and

[0033]FIG. 9 is a flowchart illustrating a signal processing method for a
digital broadcast transmitter according to an embodiment of the present
invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034]Reference will now be made in detail to the present embodiments of
the present invention, examples of which are illustrated in the
accompanying drawings, wherein like reference numerals refer to the like
elements throughout. The embodiments are described below in order to
explain the present invention by referring to the figures. Also,
well-known functions or constructions are not described in detail since
they would obscure the invention in unnecessary detail.

[0035]FIGS. 3 and 4 illustrate the structure of an MPEG packet according
to the standard of an MPEG system that is used in the ASTC Digital
Television Standard. As illustrated in FIG. 3, the MPEG packet includes a
Sync_Byte, a 1 bit transport packet error indicator, a 1 bit payload unit
start indicator, a 1 bit transport priority flag, a 13 bit PID (Packet
Identifier) value, a 2 bit transport scrambling control indicator, a 2
bit adaptation field control indicator, and 4 bit continuity counter. A
payload and/or an adaptation field follows the shown 4 bit continuity
counter.

[0036]As illustrated in FIG. 4, information such as a program clock
reference (PCR), an original program clock reference (OPCR), a splice
countdown, a transport private data length, and an adaptation field
extension length, is transmitted in an MPEG packet using an option field
such as an PCR, an POCR, a slice_point, a transport private data length,
adaptation field data, and an adaptation field extension flag. Here, the
option field may be the PCR that is used as a sync signal of a
demodulator of a receiver, OPCR used for a recording, reservation, and
playback of a program in the receiver, splice countdown that is the
number of successive macroblocks each of which is composed of four
circuit blocks, a Cr block, and a Cb block, transport private data length
that is the length of text data of a text broadcast, and adaptation field
extension length. Also shown is a 1 bit discontinuity indicator, a 1 bit
random access indicator, a 1 bit elementary stream priority indicator, a
1 byte adaptation field length, and flagged adaptation head fields.

[0037]FIGS. 5a to 5e are views illustrating diverse formats of an MPEG-2
transport stream into which a supplementary reference sequence (SRS) is
to be inserted in order to implement the transmitter according to an
aspect of the present invention. Here, for convenience in explanation,
three bytes after a sync byte of the transport stream are collectively
called a normal header, and the first two bytes of the adaptation field
are collectively called an adaptation field (AF) header. However, other
names and/or numbers of bytes can be used.

[0038]Generally, the SRS is a special known sequence in a deterministic
VSB frame that is inserted in such a way that a receiver equalizer can
utilize this known sequence to mitigate dynamic multi-path and other
adverse channel conditions. The equalizer of a receiver uses these
contiguous sequences to adapt itself to a dynamically changing channel.
When the encoder states have been forced to a known Deterministic State
(DTR), an appended pre-calculated "known sequence" of bits (SRS pattern)
is then processed immediately in a pre-determined way at specific
temporal locations at the Interleaver input of the frame. The resulting
symbols, at the Interleaver output, due to the way ATSC compatible
Interleaver functions will appear as known contiguous symbol patterns in
known locations in the VSB frame, which is available to the receiver as
additional equalizer training sequence. The data to be used in the
transport stream (TS) packets to create these known symbol sequence is
introduced into the system in a backward compatible way using existing
standard mechanisms. This data is carried in the MPEG2 adaptation field.
Hence existing standards are leveraged, and compatibility is assured.

[0039]The RS Encoder preceding the Interleaver calculates the R-S parity.
Due to resetting the TCM encoders, the calculated RS Parity bytes are
wrong and need to be corrected. Thus an additional processing step is
involved to correct parity errors in selected packets. All packets with
parity errors will have their RS parity re-encoded. A (52) segment byte
inter-leaver with unique time dispersion properties, that generates
contiguous SRS pattern is leveraged to have adequate time to re-encode
parity bytes. Required time to do this constraints the maximum number of
SRS bytes.

[0040]FIG. 5a shows the structure of an MPEG-2 packet data of a basic form
in a VSB system using an SRS. This MPEG-2 packet data includes a normal
header part composed of a one-byte sync signal and a three-byte PID
(Packet Identity), a two-byte adaptation field (AF) header including
information about the position of the stuff bytes, and stuff bytes of a
specified length N. The remaining bytes of the packet data correspond to
a normal stream that is typical payload data. Since the start position of
the stuff bytes is fixed, the information about the byte position is
expressed by information about the length of the stuff bytes. The
stuff-byte length N may be in the range of 1 to 27.

[0041]FIGS. 5b to 5e illustrate packet structures having adaptation fields
in which other information such as a program clock reference (PCR), an
original program clock reference (OPCR), a splice countdown
(splice_count), and others, are included in order to effectively use the
SRS. In these cases, the adaptation field is constructed to have a
uniform size. A part except for the AF header and information such as
PCR, OPCR, splice_count, and others, corresponds to the stuff bytes to
which the SRS is to be inserted. It is understood that, in addition to
the packet structures shown in FIGS. 5b through 5e, there are multiple
ways in which to construct a transport stream packet having a stuff
region into which the SRS is inserted in an area other than an area for
the option field of the adaptation field according to aspects of the
invention.

[0042]FIG. 6a is a block diagram illustrating the construction of a
digital broadcast transmitter according to an embodiment of the present
invention. Referring to FIG. 6a, the digital broadcast transmitter
includes a TS multiplexer (MUX) 310, a TS post multiplexer (MUX) 320, a
randomizer 330, an SRS insertion unit 340, an RS encoder 350, a data
interleaver 360, a trellis encoder 370, a backward compatibility parity
generator 380, and a multiplexer 390. The TS MUX 310 receives a video
stream and an audio stream, and constructs the existing MPEG transport
stream packet. The TS post MUX 320 forms a stuff region for inserting SRS
data into the transport stream packet output from the TS MUX 310, and
outputs the MPEG transport stream. Examples of the stream are shown in
FIGS. 5a to 5e (but not limited to) by properly moving positions such as
the PCR, OPCR, slice countdown, transport private data length, adaptation
field extension length, and other like data.

[0043]The randomizer 330 randomizes the input MPEG-2 transport stream data
in order to heighten the utility of the allocated channel space. The SRS
insertion unit 340 generates the SRS. The SRS is a specified sequence
(such as a training sequence) having a specified pattern prearranged
between the transmitter side and the receiver side. The SRS insertion
unit 340 replaces the stuff bytes in the stuff-byte position of the
randomized data with the SRS. Since the SRS is distinguishable from the
payload data, the pattern of which is transmitted/received, the SRS can
be easily detected and used for the synchronization and the equalization
at the receiver side.

[0044]The RS encoder 350 adds a parity of specified bytes to the packet
when the stuff bytes are exchanged in the packet by the SRS insertion
unit 340 by performing an RS encoding of the packet data in order to
correct errors occurring due to the channel. The interleaver 360
interleaves the data packet, to which the parity output from the RS
encoder 350 is added, in a specified pattern. The trellis encoder 370
converts the data output from the interleaver 360 into data symbols, and
performs a symbol mapping of the data symbols through a trellis encoding
at a 2/3 rate.

[0045]According to an aspect of the invention, the trellis encoder 370
initializes the value temporarily stored in its own memory device to a
specified value. For example, the initialized value can be a "00" state.
Whatever the value, the initialization is at a start point of the SRS.
The trellis encoder 370 performs the trellis encoding of the data. Also,
the trellis encoder 370 outputs a value for initializing the memory to
the backward compatibility parity generator 380, receives a new parity
generated by the backward compatibility parity generator 380, and
replaces the corresponding existing parity with the received new parity
such that the trellis encoding is performed with the new parity received
from the backward compatibility parity generator 380.

[0046]The output of the trellis encoder 370 and the next memory state are
affected by the previous memory value. That is, if the previous input is
changed, an input to be used for the initialization is changed. If the
parity of the packet corresponding to the initialization area precedes
the initialization area, the input value previously used to initialize
the memory of the trellis encoder 370 is changed due to the newly
generated parity. In this case, the initialization may not be performed,
or an accurate parity cannot be generated using the corrected
initialization value. Accordingly, in order to prevent the parity of the
initialization packet from preceding the initialization area, according
to an aspect of the invention the maximum number of used stuff bytes
becomes 27 according to an aspect of the invention. However, it is
understood that, for other types of packets divided into other numbers of
segments, other maximum numbers of used stuff bytes can be imposed.

[0047]According to an aspect of the invention, the backward compatibility
parity generator 380 generates the new parity by performing an RS
encoding of the MPEG-2 packet input from the RS encoder 360 (i.e., re-RS
encodes the RS encoded MPEG-2 packet) using the memory initializing value
input from the trellis encoder 370. The backward compatibility parity
generator 380 transmits the generated parity to the trellis encoder 370.
It is understood, however, that if backward compatibility is not need,
the generator 380 need not be included.

[0048]The MUX 390 multiplexes the trellis-encoded packet, the segment sync
signal, and the field sync signal by inserting the segment sync signal
and the field sync signal into the trellis-encoded packet. The modulator
(not illustrated) performs a VSB modulation of the packet into which the
segment sync signal and the field sync signal have been inserted, and
performs an up-converting of the modulated packet into an RF channel band
signal to transmit the RF channel band signal.

[0049]FIG. 6b is a block diagram illustrating the construction of a
digital broadcast transmitter according to another embodiment of the
present invention. In this embodiment, a TS post MUX 420 directly
receives audio and video inputs without passing through a TS MUX, and
performs the same operation as the construction of FIG. 6a. In this case,
the TS post MUX 420 is not added to the TS MUX for the SRS VSB, but is
considered as a new TS MUX for the SRS VSB.

[0050]Consistent with FIG. 6a, the randomizer 430 randomizes the input
MPEG-2 transport stream data in order to heighten the utility of the
allocated channel space. The SRS insertion unit 440 generates the SRS
that is a specified sequence having a specified pattern prearranged
between the transmitter side and the receiver side, and replaces the
stuff bytes in the stuff-byte position of the randomized data by the SRS.
The RS encoder 450 adds a parity of specified bytes to the packet of
which the stuff bytes are exchanged by the SRS insertion unit 340 by
performing an RS encoding of the packet data in order to correct errors
occurring due to the channel. The interleaver 460 interleaves the data
packet, to which the parity output from the RS encoder 350 is added, in a
specified pattern. The trellis encoder 470 converts the data output from
the interleaver 360 into data symbols, and performs a symbol mapping of
the data symbols through a trellis encoding at a 2/3 rate.

[0051]As shown, the trellis encoder 470 initializes the value temporarily
stored in its own memory device to a specified value (for example, to a
"00" state) at a start point of the SRS, and performs the trellis
encoding of the data. Also, the trellis encoder 470 outputs a value for
initializing the memory to the backward compatibility parity generator
480, receives a new parity generated by the backward compatibility parity
generator 380, and replaces the corresponding existing parity by the
received new parity.

[0052]The output of the trellis encoder and the next memory state are
affected by the previous memory value. That is, if the previous input is
changed, an input to be used for the initialization is changed. If the
parity of the packet corresponding to the initialization area precedes
the initialization area, the input value previously used to initialize
the memory of the trellis encoder 470 is changed due to the newly
generated parity. In this case, the initialization may not be performed,
or an accurate parity cannot be generated using the corrected
initialization value. Accordingly, in order to prevent the parity of the
initialization packet from preceding the initialization area, the maximum
number of used stuff bytes becomes 27.

[0053]The backward compatibility parity generator 480 generates the parity
by performing an RS encoding of the MPEG-2 packet input from the RS
encoder 460 by using the memory initializing value input from the trellis
encoder 470, and transmits the generated parity to the trellis encoder
470. However, it is understood that the generator 480 is not required in
all aspects of the invention.

[0054]The MUX 490 multiplexes the trellis-encoded packet, the segment sync
signal, and the field sync signal by inserting the segment sync signal
and the field sync signal into the trellis-encoded packet. The modulator
(not illustrated) performs a VSB modulation of the packet into which the
segment sync signal and the field sync signal have been inserted, and
performs an up-converting of the modulated packet into an RF channel band
signal to transmit the RF channel band signal.

[0055]FIG. 7 is a view illustrating an example input type of an MPEG
packet, whereby the SRS VSB can be efficiently operated, according to
aspects of the present invention. 312 MPEG packets are contained in one
VSB field. The packets that include information such as PCR, OPCR, splice
countdown, transport private data length, and adaptation field extension
length, among the 312 packets, can be input in specified positions as
shown in the drawing. The position of the option field, for example, when
312 segments are divided in the unit of 52 segments, can be expressed as
follows:

[0061]The shape of an MPEG packet as shown in FIG. 5 and the position of
an MPEG packet as shown in FIG. 7 can be modified in diverse forms in
order to efficiently use the SRS VSB.

[0062]FIG. 8 is an exemplary view illustrating the structure of an
interleaved packet according to an embodiment of the present invention.
Since MPEG information such as the PCR should be received as it is for
the compatibility, it cannot be used for the initialization or SRS
pattern. Accordingly, by transmitting the MPEG information using the
transport stream part that does not initialize the trellis encoder 370,
the loss can be reduced.

[0063]As shown in FIG. 7, when PCR or OPCR is used in the position 52n+15,
5 bytes among 6 bytes of PCR or OPCR are used in empty parts where the
known symbol is not used, and this causes a loss of the known symbols
only for one byte (i.e., 4 symbols) without any training loss occurring.
Also, in the case of transferring information less than 5 bytes, no loss
of the known symbols occurs. In FIG. 7, the splice_count is transmitted
in the position 52n+19. By transmitting the splice_count through the
empty part where the known symbol is not used as shown in FIG. 8, the
splice_count can be transmitted without any loss of the known symbols. In
the case of using the MPEG packet having the above-described structure,
the receiver uses the SRS region except for the OPCR and PCR regions as a
training sequence, and particularly, known values for the equalizer (such
as the equalizer 230) and/or the forward error correction decoder (such
as the decoder 240).

[0064]Hereinafter, an embodiment of a method for compatibly operating the
SRS VSB when no TS post MUX exists will be explained. When the MPEG
packet is input to the data randomizer 330, the randomizer 330 judges
whether an adaptation field exists using the adaptation field control
flag of FIG. 3. As shown, the adaptation field control flag of FIG. 3 has
a flag for reserved (00), a flag for no adaptation field, payload only
(01), a flag for adaptation field only, no payload (10), and a flag
adaptation field followed by payload (11). If the adaptation field
exists, the data randomizer 330 judges whether the OPCR, splicing_point,
transport_private_data, and adaptation_field_extension exist using the
flag as shown in FIG. 4. If even one flag exists, it passes the
corresponding packet without performing the stuff-byte replacement.

[0065]In this case, the trellis encoder 370 and the backward compatibility
parity generator 380 of FIG. 6A process the packet in the existing VSB
processing manner, without performing the RS re-encoding and the memory
initialization of the training sequence. In this process, the packet
carrying the information is not changed and thus can be transmitted
without any distortion.

[0066]The transmitter can transmit, using a reserved part, information
about the change of the training region by the transmission of such
information to the receiver. Also, the receiver uses the information
about the training region as the known values for the equalizer and the
forward error correction by using the information as the training
sequence.

[0067]FIG. 9 is a flowchart illustrating a signal processing method for a
digital broadcast transmitter according to an embodiment of the present
invention. Referring to FIGS. 6a and 9, the TS MUX 310 receives a video
stream and an audio stream, and constructs the transport stream packets.
The TS post MUX 320 constructs the transport stream packet that includes
the stuffing region for the insertion of the known SRS data (S910). The
randomizer 330 randomizes the packet that includes the stuffing region
(S920). The SRS insertion unit 340 inserts the SRS signal into the
stuffing region of the randomized packet (S930).

[0068]The RS encoder 350 adds the parity to the packet into which the SRS
signal has been inserted in order to correct an error occurring due to
the channel (S940). The interleaver 360 interleaves the packet to which
the parity has been added (S950). The trellis encoder 370 initializes its
own memory at a start position of the SRS signal, and performs a trellis
encoding (S960). The backward parity generator 380 receives a packet to
which the parity has been added through the RS encoder 350 in operation
S940 and a packet encoded through the trellis encoder 370, and generates
a compatibility parity on the basis of the packets (S970). The trellis
encoder 370 receives the compatibility parity from the backward
compatibility parity generator 380, replaces a part corresponding to the
compatibility parity among the parities added by the RS encoder 350 by
the generated compatibility parity, and uses this parity to perform the
trellis encoding in operation S960.

[0069]The multiplexer 390 inserts the segment sync signal and the field
sync signal into the trellis-encoded packet (S980), and the modulator
performs a VSB modulation and an RF conversion of the packet to transmit
the VSB-modulated and RF-converted packet (S990).

[0070]While described as a stream including audio and video, it is
understood that the stream can include other data according to aspects of
the invention.

[0071]As described above, according to aspects of the present invention,
the receiving performance of the digital broadcast receiver can be
improved even in an inferior multi-path channel by constructing an
adaptation field that includes a stuff-byte region in an MPEG-2 transport
stream packet, and inserting an SRS signal into the stuff-byte region in
the digital broadcast transmitter, and by detecting the SRS signal from
the received signal and using the detected SRS signal for the
synchronization and the equalization in the digital broadcast receiver.

[0072]According to aspects of the present invention, a system, which is
compatible with the existing American type digital broadcast
transmitting/receiving system and which operates efficiently, is
provided. While described in terms of a broadcast signal sent through air
or cable, it is understood that, the transmission can be made through
recording on a medium for delayed playback in other aspects of the
invention.

[0073]While not required in all aspects, it is understood that aspects of
the invention can be implemented as hardware, software or combinations
thereof. Although a few embodiments of the present invention have been
shown and described, it would be appreciated by those skilled in the art
that changes may be made in this embodiment without departing from the
principles and spirit of the invention, the scope of which is defined in
the claims and their equivalents.